After a well has been drilled and completion is accomplished by cementing a casing string in the well, various operating procedures are performed in the cased well over a period of time. For instance, equipment may be installed in the well to operate in a first state of affairs for a long interval. Nevertheless, as the well ages, the producing formation becomes depleted and it becomes necessary to change, modify or alter the location or nature of the equipment installed in the completed well. Consider as an example a well which passes through two or three different productive formations. If the most productive formation occurs at a relatively shallow horizon, it may be appropriate to pack off that strata with a bridge plug or packer below that formation, perforate casing at that formation, and isolate that formation with a second packer above the formation. The packers are installed in the well by wedging the packers against the casing. Ultimately, should that formation be depleted, it will then be necessary to remove the two packers, plug the various perforations, and direct completion procedures to another formation at a greater depth. Then, it will be necessary to mill out or otherwise remove the two packers. When this is needed, the packers are milled to destroy them. They create substantial debris. The debris from destruction of the packers gets in the way of subsequent procedures.
It is desirable to keep the cased well borehole free of the debris so that subsequent well completion can be accomplished without impediment from the scattered pieces of debris which are collected along the cased well borehole. One way of doing this is to simply drill through the packers and let the debris fall to a great depth in the well. This is acceptable if the well is sufficiently deep. However, there are times when that is not an acceptable process. It may be important to remove the debris. The procedure for accomplishing this is set forth hereinbelow and especially utilizes the reverse circulating tool set forth in the disclosure which is U.S. Pat. No. 5,176,208. That is a device which enables well completion procedures to be carried out with a view of collecting the trash and debris in the tool. However, it requires use of the reverse circulation tool in conjunction with cooperative apparatus so that the correct and varied removal procedures can be implemented. More specifically, the reverse circulation tool of the present disclosure is able to collect debris with cooperative equipment so that the necessary retrieval procedure can be implemented without difficulty.
One approach in the use of this tool involves utilization of an external rubber skirt which isolates fluid flow in the annular space on the exterior of the reverse circulating tool. This external flow cooperates with a burning shoe which cuts metal parts on the interior of the cased well and helps collect that debris or junk in the tool interior. In another aspect, the reverse circulation tool of the present disclosure can be used with a tool supported packoff rubber skirt to divert and assure external fluid flow in the annular space around the tool downwardly and back up through the tool. This can be used with a finger shoe so that debris is also collected and held in the circulating tool of the present disclosure. In another aspect, junk collected in the bottom of a cased well can be collected using an alternate type shoe fitted at the lower end of the reverse circulating tool. This is particularly able to be used to remove debris from the well borehole. In addition, it can be used adjacent to perforations through the casing so that the casing adjacent the perforations can be washed. This will typically remove some of the trash and other debris in the perforations to a certain depth. Other procedures can also be implemented as set forth hereinbelow for the primary purpose of removing the junk that is collected in the well after destruction of items in the cased well.